What happens in the brain when you get ‘knocked out’

In the blink of an eye, the right punch can send you flying out cold before if you even hit the floor. That’s something any professional boxer hopes for or fears if he happens to be on the wrong end of a punch. But what happens in the brain when it suffers such trauma?

The deceptively simple answer is that the brain is very fragile. It’s almost entirely made out of blood vessels and nerves. We’re talking about a soft, mushy mass of tissue that controls all neural higher functions and commands you as a person. But despite this shortcoming, the brain is remarkably resilient at receiving trauma and ‘blackouts’ help in this respect, like a sort of defense mechanism.

Credit: University of Rochester

All this mushy mass is floating in a clear, colorless body liquid called the cerebrospinal fluid which protects the brain from coming into contact with the skull. If the punch is good enough, it could cause the brain to slam into the skull from the acceleration caused by the blow and the deceleration caused by the muscles and tendons trying to prevent the head from spinning further.

When the brain slams into the skull, you get trauma — brain cells literally start dying from the physical impact. This happens multiple times as the brain bounces off the walls of the skull on and off until the energy from the blow is dissipated.

The trauma causes an overwhelming number of neurotransmitters to fire all at the same time. This behavior induces a form of nervous system overload, causing a system crash — a form of temporary paralysis.

Another mechanism that causes loss of consciousness has to do with how blood flows to the brain. A reflex area in the brain called the sinus regulates the flow of blood and oxygen to the head, but a good knock on the jaw could jolt the sinus. This lightning fast altering of the blood and oxygen flow can be enough to cause a blackout.

It can take anything from a couple of seconds to a couple of minutes before a person can regain consciousness. It all depends on the severity of the blow. Some people can shake it off and are only left with a headache. Others less fortunate can incur serious medical problems from the concussion, like cerebral bleeding and even death.

The blow from a KO-quality punch often leaves its victims with memory problems, mood changes, confusion, and a slower information processing speed. If you suffer repeated blows, like athletes in contact sports often do, it’s possible to lose brain volume in the frontal and posterior regions of the brain as white matter dies. Chronic damage such as personality changes and dementia are some of the risks football athletes or boxers face.

A professional boxer’s punch can pack 400 kilograms of force, but you don’t need to hit that hard to knock someone out. Rather, the targeted body parts are far more important. That’s because, as outlined earlier, knockouts happen when the brain rotates very fast. Someone could get hurt pretty bad if hit at the top of the head but he won’t go unconscious. The same blow to the chin or side of the jaw area is a different matter.

If you’re unfortunate enough to suffer a concussion, either after a fight or accident, the best medicine is rest. If the headaches don’t stop after a couple of days, visit a doctor immediately.